A hydraulically damped mounting device is known in which the anchor part for one part of the vibrating machinery is in the form of a hollow sleeve with the other anchor part in the form of a rod or tube extending approximately centrally and coaxially of the sleeve. Resilient walls then join the sleeve and the tube and define two chambers connected by a passageway. The chambers are filled with hydraulic fluid, and the movement of the fluid from one chamber to the other through the passageway damps the vibration of the parts of the machinery attached to the respective anchor points.
Mounting devices of this type, in which there is a first anchor part, for example in the form of a tube, within a second anchor part in the form of a sleeve, with the sleeve and tube being connected by resilient walls, are desirable because they permit a compact construction, all parts being enclosed within the sleeve. This design, employing orifice damping via a short passage between the upper and lower fluid chambers would not allow a long tuned fluid column between the chambers to oscillate in the laminar flow region, thus would contribute to noise transmission.
Another device is known wherein a long damping channel has been provided to dampen low frequency high amplitude vibrations. At one end of the damping channel there is provided a diaphragm bellows displacement chamber to move the fluid through the channel as opposed to moving the spring rubber for the displacement. This bellows plays no part in the springing action of the mount. The device also employs a high frequency external decoupler between the damping fluid and the atmosphere. This type of external decoupler not only requires the employment of an adequate seal to prevent leakage of the fluid through the diaphragm used in the decoupler, but also fails to provide for the positive pressure of fluid to counteract the high frequency vibrations occurring in the device, rather relying upon the negative pressure for vacuum created as the fluid moves away from the diaphragm of the decoupler. In addition, the existence of the external decoupler contributes to the greater bulkiness of the device.
It is therefore an object of the present invention to provide a bush type mounting device having a more compact and simpler construction. It is a further object of the invention to provide a bush type mounting device with inertial hydraulic damping. It is a still further object of the present invention to provide such a device with high frequency decoupling.
The objects have been met in accordance with the present invention by providing a bush type mounting device having inertial hydraulic damping and internal hydraulic decoupling. Such a device comprising an outer sleeve: and intermediate sleeve radially inward from said outer sleeve defining an annular space therebetween; an inner metal portion formed within the intermediate sleeve; a rubber spring bonded to an outer surface of the inner metal on one side of the rubber spring and to an inner surface of the intermediate sleeve on another side of the rubber spring, diametrically located to divide the intermediate sleeve into a lower fluid chamber and an upper fluid chamber, each containing a fluid: an inertial damping channel located within the annular space: and a means for hydraulically decoupling the fluid between the lower chamber and the upper chamber.